Effects of energy deficit, dietary protein, and feeding on intracellular regulators of skeletal muscle proteolysis

FASEB J. 2013 Dec;27(12):5104-11. doi: 10.1096/fj.13-239228. Epub 2013 Aug 21.

Abstract

This study was undertaken to characterize the ubiquitin proteasome system (UPS) response to varied dietary protein intake, energy deficit (ED), and consumption of a mixed meal. A randomized, controlled trial of 39 adults consuming protein at 0.8 (recommended dietary allowance [RDA]), 1.6 (2×-RDA), or 2.4 (3×-RDA) g · kg(-1) · d(-1) for 31 d. A 10-d weight maintenance (WM) period was followed by 21 d of 40% ED. Ubiquitin (Ub)-mediated proteolysis and associated gene expression were assessed in the postabsorptive (fasted) and postprandial (fed; 480 kcal, 20 g protein) states after WM and ED by using muscle biopsies, fluorescence-based assays, immunoblot analysis, and real-time qRT-PCR. In the assessment of UPS responses to varied protein intakes, ED, and feeding, the RDA, WM, and fasted measures served as appropriate controls. ED resulted in the up-regulation of UPS-associated gene expression, as mRNA expression of the atrogenes muscle RING finger-1 (MuRF1) and atrogin-1 were 1.2- and 1.3-fold higher (P<0.05) for ED than for WM. However, mixed-meal consumption attenuated UPS-mediated proteolysis, independent of energy status or dietary protein, as the activities of the 26S proteasome subunits β1, β2, and β5 were lower (P<0.05) for fed than for fasted. Muscle protein ubiquitylation was also 45% lower (P<0.05) for fed than for fasted, regardless of dietary protein and energy manipulations. Independent of habitual protein intake and despite increased MuRF1 and atrogin-1 mRNA expression during ED, consuming a protein-containing mixed meal attenuates Ub-mediated proteolysis.

Trial registration: ClinicalTrials.gov NCT01292395.

Keywords: caspase-3; high-protein diets; negative energy balance; ubiquitin proteasome.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Adolescent
  • Adult
  • Body Weight
  • Caloric Restriction*
  • Dietary Proteins / metabolism*
  • Fasting
  • Female
  • Humans
  • Male
  • Muscle Proteins / genetics
  • Muscle Proteins / metabolism
  • Muscle, Skeletal / metabolism*
  • Polycomb Repressive Complex 1 / genetics
  • Polycomb Repressive Complex 1 / metabolism
  • Proteasome Endopeptidase Complex / metabolism
  • Proteolysis*
  • Recommended Dietary Allowances
  • SKP Cullin F-Box Protein Ligases / genetics
  • SKP Cullin F-Box Protein Ligases / metabolism
  • Transcription, Genetic
  • Ubiquitin / metabolism
  • Ubiquitination

Substances

  • Dietary Proteins
  • Muscle Proteins
  • Ubiquitin
  • FBXO32 protein, human
  • Polycomb Repressive Complex 1
  • RING1 protein, human
  • SKP Cullin F-Box Protein Ligases
  • Proteasome Endopeptidase Complex

Associated data

  • ClinicalTrials.gov/NCT01292395